Two-toned echolocation calls from Molossus molossus in Cuba

Molossus molossus from Cuba uses narrowband search signals that typically a re emitted in a series of pairs with a signal of lower frequency (mean peak frequency = 34.1 kHz) followed by a signal of higher frequency (39.7 kHz). Both frequencies fall into the most sensitive region of a previously publi shed audiogram of M. molossus. Because there is no overlap in frequency bet ween the two signals of one pair, pairing may allow the bat to process echo es of one call while emitting the second call. This would extend the duty c ycle of temporal scanning by using two separate frequency channels in its a uditory system to analyze calls.